Advances in technology have led to a proliferation of small, handheld computing devices such as smart phones, personal digital assistants (PDAs), and tablet computers. Such devices typically include a large touch screen that functions as both a display and input device. In order to maximize the surface area of the touch screen, the touch screen typically extends close to the side edges of the device. A graphical user interface is displayed on the touch screen. The user interacts with the graphical user interface by touching the screen with a stylus, pen or finger. A processor detects the position of the touch input and determines an appropriate action to take based upon position of the touch and the position of elements in the graphical user interface. Multi-touch screens are capable of detecting and tracking multiple, simultaneous touch inputs such as sliding two fingers on a touch screen. The multi-touch gestures are then translated into commands to be executed by the processor.
Handheld tablets are frequently used as point of sale (POS) terminals in retail settings. When using a tablet in a retail store as a POS device, the user typically holds the device in one hand and uses the opposite hand for interacting with the touch screen. It is common for the thumb or fingers on the hand holding the device to inadvertently touch the touch screen. Such unintentional touch inputs by the user may cause unexpected results, for example, where a user unintentionally touches an interactive element in the graphical user interface.
Palm rejection technology is known for detecting unintentional touches and defining an active zone on the touch screen display that excludes the area where unintentional touch input occurs. This excluded area is referred to as the rejection zone. Touch inputs within the rejection zone are ignored by the application. Currently, there is no convenient method of enabling a user to define the active zone of the display in a way that accommodates changes in the way that the tablet is held by the user.